a) Field of the Invention
The present invention relates to cruise control apparatus and method for an automotive vehicle which control a vehicle speed to maintain the vehicle speed at a set (target) vehicle speed through a vehicular engine throttle valve.
b) Description of the Related Art
A previously proposed cruise control apparatus for the vehicle is exemplified by a U.S. Pat. No. 4,835,696.
When a main switch of the previously proposed cruise control apparatus (also called ASCD (Automatic Speed Control Device)) is turned on, a power supply of a controller of the cruise control apparatus is turned on and a self-diagnosis program stored in the controller is started to run. When, as a result of the self-diagnosis, the controller determines that the cruise control apparatus operates normally (system normal) and enables an acceptance of an input through a set switch to set a target vehicle speed.
When the set switch is operated after the acceptance of the input of the set switch is enabled, the vehicle speed at the time of operation of the set switch is set to the target vehicle speed, an indicator light is illuminated, and the cruise control of the vehicle is started.
When the main switch is turned off, the power supply of the controller is interrupted, the cruise speed control is ended, the acceptance of the input of the set switch is disabled, and the indicator lamp is turned off.
On the other hand, when the set switch is turned on before the acceptance of the input of the set switch is enabled, the controller determines a system error, does not start the cruise control, and repeatedly turns on or off the indicator lamp. Such a situation as described above occurs if the set switch falls and remains in an on state (this failure is generally called "welded (sticky) failure".
It is noted that since, in the previously proposed cruise control apparatus, the main switch is placed far away from the set switch. Hence, it is impossible to operate simultaneously the set switch and the main switch during the run of the vehicle. Hence, it is impossible for the controller to determine the system error equal to the failure such that the set switch remains in the on state in terms of the operation of the set switch.